The present invention generally relates to data storage devices. More specifically, the present invention relates to removable cartridge storage devices.
Computer backup has traditionally been performed using tape drive technologies. Tape drive technologies have been popular in the use of backup systems for a variety of reasons. One reason is that tape media has generally had the lowest cost per bit of storage. Additionally, tape devices use removable tape cartridges, which may be taken to an off-site location to provide for disaster recovery. A third reason tape devices are popular is because of the long-term archive characteristics of tape media.
As the storage capacity in stand-alone and networked computers has increased, so have the demands on backup systems. One of the current trends is the use of mechanical automation systems, such as tape cartridge autoloaders and robotic tape libraries, to expand the capacity of the backup system. The cartridge autoloaders and tape libraries hold multiple removable tape cartridges. One or more tape drives is embedded inside a storage area containing one or more magazines of tape cartridges. These systems also include a mechanical system to automate the cartridge changing operation. The mechanical system is used to load and unload the cartridges between the magazines and the tape drives.
A prior art standalone tape drive that may be used to perform data backups is illustrated in FIG. 1. The tape drive 100 includes a system controller 102. The system controller 102 includes an interface to a host computer 120. By way of example, the interface to the host computer may be Small Computer Systems Interface (SCSI), Fiber Channel (FC), or other type of communication interface. The system controller 102 also includes a microprocessor which performs data formatting for the tape medium. The tape drive 100 also includes a tape recording mechanism 104 which magnetically encodes the formatted data on magnetic tape cartridges 106, 108, 110. Tape recording mechanism 104 is also used to read data from the magnetic tape cartridges 106, 108, 110. Oftentimes, the backup of host computer may require more storage capacity than that available on a single tape cartridge 106, 108, 110. Thus, if the tape drive is not part of a tape autoloader system, an operator may be required to manually remove a tape cartridge 106 which has reached its data storage capacity, and insert a new tape cartridge 108, so that the transfer of data from host computer to magnetic tape cartridges may continue. The operator may be required to repeat this process multiple times before the backup is completed.
FIG. 2 illustrates a second prior art system that has multiple tape drives 210, 220 coupled to a host computer system 200. Both tape drives 210, 220 include system controllers 212, 222. Each of the system controllers 212, 222 has an interface to host computer system 200, such as a SCSI or FC interface. The tape drives 210, 220 additionally includes a tape recording mechanism 214, 224, which may be used to magnetically encode data on a magnetic tape cartridge 216, 226.
In some embodiments, a tape automation system, such as the tape autoloader 300 illustrated in FIG. 3 may be used to automate cartridge changing operations. The tape autoloader includes at least one tape drive 320. Multiple storage slots 311-317 may be used to house tape cartridges 301-307. In some embodiments, the storage slots 311-317 may be part of a removable magazine to facilitate the loading and unloading of cartridges.
A motorized mechanism 330 may be used to move the tape cartridges 301-307 to and from the tape drive 320. The motorized mechanism may also optionally be used to move cartridges to and from an access opening (not shown) to the tape autoloader 300, which may be used to enter and remove tape cartridges 301-307 into the tape autoloader 300. In one embodiment, the motorized mechanism 300 may include a cartridge picker arm 334 and a picker motor 332 to operate the cartridge picker arm 334. A drive motor 336 is used to drive the motorized mechanism 330.
The tape autoloader 300 has at least two interfaces 352, 354 to host computer 350. By way of example, interfaces 352, 354 may be SCSI or FC interfaces. One interface 354 is provided for each tape drive 320 included in the tape autoloader. This interface 354 may be referred to as the “data path” interface and is used to send data and tape drive commands to a system controller component of tape drive 320. In embodiments in which the tape autoloader 300 includes multiple tape drives, the data path interfaces to each tape drive may be coupled to different host computers. A second interface 352 (also called the “control path”) is used to send media changer commands to the autoloader mechanism controller 340, such as load, unload, and audit commands. The autoloader mechanism controller 340 includes electronics and software used to actuate the motorized mechanism 330 for movement of tape cartridges 301-307 and auditing of the tape autoloader 300. In some embodiments, the control path interface 352 may be coupled to a second host computer. The autoloader mechanism controller 340 may also be communicatively coupled to tape drive 320 for communications between these components. Although multiple tape drives in the tape autoloader 300 may be operated in parallel, the mechanical system 330 used to load and unload cartridges can only move a single cartridge at a time. Additionally, each tape drive 320 has its own system controller which requires a separate “data path” interface to a host computer 350.
Another prior art system that may be used to perform backups is illustrated in FIG. 4. FIG. 4 illustrates a virtual tape system 400. The virtual tape system 400 uses a HDD or array of HDDs 404 for storage of data. A system controller 402 may provide emulation of tape interface commands to enable the virtual tape system to interface to a backup software application using a native tape command set. Thus, the system controller 402 may communicate with a host computer 410 over an interface using SCSI or FC tape commands. The system controller 402 also formats received data to a disk format for recordation on HDDs 404. The HDDs may be in a RAID or JBOD configuration and may be logically partitioned to create the illusion of multiple discrete data cartridges to which the data is recorded. However, in this type of system, the virtual data cartridges are not physically separable from one another since they are all contained in a single disk or disk array. Thus, the data cannot be removed to an offsite location for disaster recovery protection.